This invention relates to an improved navigation system, such system including processing means, a graphical display, memory, map data stored in said memory, and signal reception means for receiving one or more wireless signals by means of which the processor can determine a present location of the system. Specifically, this invention is concerned with an improved portable navigation device including all these features and operating under the control of software locally installed thereon.
Navigation systems, both portable and integrated, are well known, and becoming increasingly globally widespread. In particular, the adoption of portable navigation devices (PNDs) has been particularly rapid and in most developed countries, such devices are becoming ubiquitous, and most commonly being used in fuel-powered vehicles such as automobiles and motorbikes.
U.S. Pat. No. 5,742,922 describes an integrated vehicle navigation system and method of selecting a route for vehicle travel according to fuel consumption, such system being one which is installed in a vehicle at the time of manufacture, and is therefore not portable. The system includes an input device for selecting a destination, an antenna for receiving satellite signals and/or signals related to traffic situation, a memory, and a controller, such as a microcomputer, for determining a current vehicle position and alternative routes from the current vehicle position to the destination and for selecting from the alternative routes, according to altitude information for the routes and the traffic situation, a preferred route requiring the least fuel consumption. The method includes the steps of determining the current vehicle position based on signals received from satellites, determining the routes from the current position to the destination, and selecting from the routes the preferred route requiring the least amount of fuel consumption based on fuel consumption data entered into the system and related to the altitude differences over particular determined routes.
U.S. Pat. No. 6,591,185 describes a method for determining optimal fuel usage in a vehicle navigation system and a warning system for alerting a driver when there is insufficient fuel to reach a desired destination. In addition, there is disclosure of the making of a provision to calculate fuel usage and to alert the driver when there is insufficient fuel to reach a fuel filling station on a return trip from the desired destination. Specifically, the patent claims a method for determining fuel usage for a vehicle in a vehicle navigation system comprising the steps of entering a destination in the vehicle navigation system; calculating a first route to reach the destination; identifying a fuel filling station closest to the destination; calculating approximate fuel usage required for the vehicle to reach the destination by the first route plus fuel usage to reach the fuel filling station closest to the destination after reaching the destination; comparing the calculated fuel usage required for the vehicle to reach the destination by the first route plus fuel usage to reach the fuel filling station closest to the destination after reaching the destination with a quantity of fuel remaining in the vehicle; and displaying a message that the destination and the fuel filling station closest to the destination cannot be reached when the fuel remaining is less than said calculated fuel usage required for the vehicle to reach the destination by the first route plus fuel usage to reach the fuel filling station closest to the destination after reaching the destination.
The above patents relate to integrated navigation systems, and are not concerned with portable navigation devices (PNDs). PNDs are fundamentally different in that they are not typically integrated into the vehicle and in general are not in communication with the subsystems of the vehicle, nor can they typically derive any information therefrom, but function more as stand alone devices, albeit provided with certain information provided by the user at start-up and during conventional use. More recently, PNDs have begun to receive different types of wireless signal which not only provide information by means of which the present global position of the device can be determined, but also provide an indication of traffic congestion along a particular route. By means of such information it is possible for the device to perform a route recalculation to offer the driver of a vehicle alternatives which both avoid the congested section of the route and thus potentially reduce the time in which the driver will reach his desired destination, and/or render the driving experience less stressful by reducing frustration arising from being stationary for any length of time, and thus making the travel along a particular route more continuous.
For example, U.S. Pat. No. 6,711,498 describes a method for operating a navigation system for a vehicle, particularly for a motor vehicle, in which a travel route is calculated in a computing circuit on the basis of a location of the vehicle, a digitally stored map and a destination location, and is made available to the vehicle driver as an acoustical and/or visual message, where traffic information relevant to the travel route may be acquired via a receiver unit and a new travel time t resulting therefrom is calculated for the existing travel route with the aid of a predefined weighting factor Gf for a disturbance event and the length of a traffic disturbance Ls, and a travel time ta is calculated in the same manner for an alternative route, and in the event that the travel time ta of the alternative route is shorter than the travel time t of the travel route, is indicated to the vehicle driver. A correction value K for the weighting factors Gf is ascertained on the basis of the length of the traffic disturbance Ls, and a corrected weighting factor Gk is ascertained as a function of the correction value Kw and is used for calculating the new travel time t.